Data Collection for the Calculation of Phase Equilibria

Abstract

Data collection for the calculation of phase equilibria is discussed, with reference to the Al‒Ni‒Re system. Since there were conflicting data for the Al‒Re system and no data at all for the ternary system, an extensive experimental programme was initiated using SEM with EDS, and XRD. X-ray data were modelled for the likely structures of some phases. Experimental results indicated that a previously unreported binary eutectic reaction forming Al2Re3 and Al3Re was found at ∼ 34at.% Re. With the exception of Al12Re (which was only found as a minor, finely divided component), all intermetallic phases were demonstrated to have a composition range between 1.5 and ∼5 at.%. In the Al‒Ni‒Re ternary system, (Re) had the greatest solubility. The Al3Re and Al6Re phases extended within the ternary to ∼6 at.% Ni, whereas AlNi and AlRe2 showed ∼3 at.% extension. The remaining phases had very much lower solubility limits. The liquidus surface was derived from the sequence of solidification. Since these findings were largely deduced from metallographic studies, problems associated with the interpretation of microstructures were discussed in general terms.